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'99 V70 2.4 NA - O2 sensors battle

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
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Re: '99 V70 2.4 NA - O2 sensors battle

Post by abscate » Thu Mar 19, 2020 10:07 am

The rear OS X should sit at about 0.5VDC while running.

The front one is complex - it is a pulsed signal corresponding the varying oxygen level in the exhaust

Volvo doesn't have a set of specs for that in Alldata at least.

I can probably measure it on the S70 later today
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Re: '99 V70 2.4 NA - O2 sensors battle

Post by fszczesniak » Thu Mar 19, 2020 10:40 am

Precat should be able to jump between 0.1 and 0.9v, but what I mean is, what onboard voltage should precat get from battery/ECU... If it won't have at least 10.5v, it won't operate correctly (source - "Hella" lambda troubleshooting website)

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Re: '99 V70 2.4 NA - O2 sensors battle

Post by Clemens » Thu Mar 19, 2020 3:06 pm

I habe no clue about the O2 sensor issue, but an old coolant temp sensor can cause abnormally gigh fuel consumption. But then, you seem to have traced it down to the O2 already.
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Re: '99 V70 2.4 NA - O2 sensors battle

Post by fszczesniak » Thu Mar 19, 2020 11:12 pm

My sensor is old, but I had visually inspected it not so long ago when I installed a new coolant tank and never had any problems with engine temp readings

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Re: '99 V70 2.4 NA - O2 sensors battle

Post by fszczesniak » Sat Mar 21, 2020 12:17 pm

I have noticed lately that my battery is always charging with 13.6V, even after roadtrips (the battery is new) - does it add anything to the problem?

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Re: '99 V70 2.4 NA - O2 sensors battle

Post by misha » Sat Mar 21, 2020 1:34 pm

Measure directly on alternator with multimeter,BUT after about 30 min of driving and WITHOUT turning the engine off.

Red probe on b+ and black one on alternator housing.

If there is 13.9-14.0v with headlights ON and battery terminals still shows 13.6v,you have a voltage drop.

If you have a voltage drop we will proceed in further investigation.
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Re: '99 V70 2.4 NA - O2 sensors battle

Post by fszczesniak » Sat Mar 21, 2020 1:45 pm

Aye, will do and report as soon as possible

Edit: as suspected, the alternator is giving around 13,9-14V, and battery is getting 13,8V (lights ON, car driven for about 30 minutes)

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Re: '99 V70 2.4 NA - O2 sensors battle

Post by fszczesniak » Sat Apr 04, 2020 2:11 pm

vida dice data - hot idle
- o2 sensor precat fixed at 0,98v
- o2 sensor postcat fixed at 0,85v

running really rich or what?

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Re: '99 V70 2.4 NA - O2 sensors battle

Post by misha » Sat Apr 04, 2020 2:54 pm

fszczesniak wrote: ...Edit: as suspected, the alternator is giving around 13,9-14V, and battery is getting 13,8V (lights ON, car driven for about 30 minutes)
You are in accepted limits of voltage drop 0.2v....charging system is healthy.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

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Re: '99 V70 2.4 NA - O2 sensors battle

Post by misha » Sat Apr 04, 2020 2:56 pm

fszczesniak wrote:
Sat Apr 04, 2020 2:11 pm
vida dice data - hot idle
- o2 sensor precat fixed at 0,98v
- o2 sensor postcat fixed at 0,85v

running really rich or what?
Front o2 sensor should go up & down with voltage.
Do you have black smoke from the exhaust at idle?
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

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